Initial Reports of the Deep Sea Drilling Project - Volume 39

This volume covers Leg 39 of the cruises of the Drilling Vessel Glomar Challenger. Unlike most recent Deep Sea Drilling Project cruises, Leg 39 was not scientifically planned as a "theme" cruise, on which a number of sites are drilled to address a single scientific problem area. Rather, the general geographic area for drilling was dictated largely by logistics, since it was necessary to get Glomar Challenger from her recently completed Norwegian Sea drilling during the Northern Hemisphere summer to Cape Town in time to begin a third season of Antarctic and Southern Ocean drilling during the Southern Hemisphere summer. In order to optimize the ratio of drilling time to steaming time on the long cruise from Amsterdam to Cape Town, a cruise track to the western part of the South Atlantic was indicated. The result was the longest cruise to date in the DSDP program, both in terms of miles (9985) and days (72). Leg 39 scientific goals were to: 1) drill a presumed section of oceanic layer 3 in the offset region of the Vema Fracture Zone (Site 353); 2) collect a biostratigraphic section on the Ceará Rise (Site 354), determine the nature and age of a prominent reflector there, and determine the nature and age of basement; 3) date basement between magnetic anomalies 32 and 33 in the Argentine Basin (Site 358), and 33 and 34 in the Brazil Basin (Site 355); 4) obtain as complete sedimentary sections as time would permit at the Ceará Rise, Brazil Basin, the Argentine Basin, Sào Paulo Plateau (Site 356), and Rio Grande Rise (Site 357) to support the major objective of the cruise, improving our knowledge of paleocirculation changes and the overall geologic history of the South Atlantic Ocean; 5) determine the nature and age of prominent reflecting Horizons A and B in the Argentine Basin. Glomar Challenger departed Amsterdam on 6 October 1974 and arrived in Cape Town at first light on 17 December 1974. Glomar Challenger traveled 9895 miles and drilled 11 holes on seven sites.